Place butter, cream cheese, vanilla extract, and lemon juice into the work bowl of a large stand mixer fitted with whisk attachment; beat mixture on medium speed until smooth.
Scrape down the attachment and sides of bowl; add confectioners' sugar to butter mixture. Mix at low speed until confectioners' sugar begins to incorporate into butter mixture. Raise mixer speed to high and beat until frosting is light and fluffy, scraping sides occasionally, about 3 minutes. Frosting will set up and become firmer when refrigerated.
